1. Field of the Invention
The present invention relates to magnetic recording media comprising magnetic thin films obtained by vapor deposition as magnetic recording layers. More particularly, this invention relates to vapor deposition type magnetic recording media having excellent running properties and abrasion resistance.
2. Description of the Prior Art
There have heretofore been widely employed as magnetic recording media obtained by dispersing powder magnetic materials such as oxide magnetic powders, ferromagnetic alloy powders and the like, e.g. .gamma.-Fe.sub.2 O.sub.3, .gamma.-Fe.sub.2 O.sub.3 doped with Co, Fe.sub.3 O.sub.4, Fe.sub.3 O.sub.4 doped with Co, Berthollide compounds of .gamma.-Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4, CrO.sub.2, etc., in an organic binder such as a vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, polyurethane resin or the like, coating the dispersion on a non-magnetic support and drying. Lately with the increased demand for high density recording, attention has been directed to the so-called metal thin film type magnetic recording media which are binderless and utilize as the magnetic recording layers ferromagnetic metal thin films formed by a vapor deposition technique such as vacuum deposition, sputtering, ion plating, etc., or a plating method such as electro plating, electroless plating etc., and a great deal of effort has been exerted toward the practical applications.
Since the former coated magnetic recording media primarily employ metal oxides having low saturation magnetization as magnetic materials, the reduction in thickness which is required for high density recording has reached its limit because it results in a reduction in signal output. Another drawback to coated media is that the production process is complicated and requires large auxiliary equipment for solvent recovery or preventing pollution. The magnetic recording media of the metal thin film type have the advantage that they can be formed as extremely thin films of ferromagnetic metals having greater saturation magnetization than the oxides in the state free from non-magnetic materials such as binders. Of the magnetic recording media of the metal thin film type, the vapor deposition type magnetic recording media which form films from the gaseous state are advantageous in that the film forming speed is rapid, the production process is simple, and the disposal of waste liquor is not necessary. However, important problems are raised with the vapor deposition type thin film magnetic recording media with respect to resistance to corrosion, impact and abrasion. In other words, in the process of recording, play back and erasing of magnetic signals, the relative movement with the magnetic head makes abrasion or damage due to contact with the magnetic head likely. The vapor deposition type magnetic recording media have heretofore suffered from wear due to the damage on contact sliding with magnetic heads. While attempts have been made to reduce wear by overcoating a polymer film of approximately 0.2 microns in thickness, due to spacing loss this reduces the output. It has also been known to coat a lubricant to reduce the friction between the magnetic head and the metal thin film and thus reduce the abrasion, but the effect imparted by coating the lubricant does not last long and upon use of the magnetic tape increased abrasion and damage of the magnetic tape can suddenly occur.